Chữ Số Lớn Nhất

#include<iostream>
#include<iomanip>
using namespace std;

void NhapSoNguyenDuong(int &num)
{
	do
	{
		cout << "\nEnter number: ";
		cin >> num;
		if ((num <= 1) || (num >= 10000000))
			cout << "\nMoi ban nhap lai";
	} while ((num <= 1) || (num >= 10000000));
}
int ChuSoLonNhat(int num)
{
	int Max = num % 10;
	int phantu;
	while (num)
	{
		num /= 10;
		phantu = num % 10;
		if (phantu > Max)
			Max = phantu;
	}
	return Max;
}
int main()
{
	int num;
	NhapSoNguyenDuong(num);
	cout << "So lon nhat trong chuoi so nhap vao la: " << ChuSoLonNhat(num) << endl;
	system("pause");
}